As an electronic medium which is an alternative to paper, display devices such as for an electronic paper are actively developed. Contrary to the conventional displays, such as a CRT and a liquid crystal display, electronic paper and the like mainly adopt a reflection type display system which uses display media made of white particles and black particles and the like, need to have a high white reflectance and a high contrast ratio, and, in addition, require a memory effect for a displayed image. It is also required to be capable of being driven under a low voltage, and, further, thin and light, and low in price. Specifically, as display characteristics, a white reflectance and a contrast ratio equivalent to those of paper are required, and there is a great demand for colorization of the display devices, such as electronic paper because, as a matter of course, the conventional paper media display full color.
Among the technologies proposed so far, as electronic paper which is capable of performing color display, there is a product in which a color filter is formed on a liquid crystal element, or the like, but this product uses a polarizing plate and therefore utilization efficiency of light is low, and only dark white color can be displayed. Further, because black color cannot be displayed, a contrast ratio is poor.
Moreover, as a bright reflection type display device, there is known an electrophoresis system whose principle is to move, without using a polarizing plate, white particles and black particles, which have been charged with electricity, by an electric field. Generally, it is said that a scattering reflectance by this electrophoresis system is a little less than 40% at most, and at present, it is required to further improve the reflectance. Particularly, when color display is performed, utilization efficiency of light is degraded due to absorption by a color layer. Therefore, bright color electronic paper is actively researched and developed.
For example, Patent Literatures 1, 2, and 3 propose electrophoresis type display elements in which charged white particles and particles whose black color state is optionally switched are moved by applying a voltage, and further, describe technologies which enable color display by disposing a color filter. However, the conventional color filter, which is used in a liquid crystal display device and the like, includes a black matrix as a shading portion, and overlapping colored pixels, and hence deteriorates the degree of brightness due to the scattered reflected light by the charged particles is partially deteriorated. Moreover, when colored layers of the color filter are formed by photolithography, in order to realize multicolor display, the same number of steps as the number of the colored layers is needed, and hence the cost of steps and the coloring resist are wastefully used.
By the way, the method of producing a color filter by an inkjet method is already well known for a liquid crystal display device and the like. Red, blue, and green coloring inks are ejected simultaneously at respective necessary points and applied to regions where pixels are formed, and cured so as to form colored layers. At this time, in order to form the colored layers with accuracy, it is necessary to preliminarily form partition walls by photolithography, and eject coloring ink to the regions which are formed by the partition walls. For example, Patent Literature 4 describes that mixture of colors between adjacent pixel regions can be avoided by maintaining the static contact angle between the coloring ink and the partition wall surface within 30 to 55°.